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Abstract

Background

In clinical practice, sleep disturbance is often regarded as an epiphenomenon of the
primary mental disorder. The aim of this study was to test if sleep disturbance, independently
of primary mental disorders, is associated with current clinical state and benefit
from treatment in a sample representative of public mental health care clinics.

Results

Sleep disturbance was, adjusted for age, gender, time in treatment, type of care,
and the presence of any primary mental disorder, associated with lower quality of
life, higher symptom severity, higher disorder severity, lower levels of functioning,
and less benefit from treatment.

Conclusion

Sleep disturbance ought to be considered a stand-alone therapeutic entity rather than
an epiphenomenon of existing diagnoses for patients receiving treatment in mental
health care.

Background

Sleep disturbance affects 50% to 80% of all patients with mental disorders and it
is currently a symptom of 19 axis I disorders
[1-3]. At the same time, it is considered to be a disorder in itself if the sleep disturbance
impairs daily functioning
[4,5]. With this diagnostic multitude, there is a possibility that clinicians regard the
sleep disturbance as an epiphenomenon that will be dissolved once the primary mental
disorder is treated and not as a valid stand-alone clinical entity
[1]. This distinction can have consequences for choice of treatment for these patients
[1] and sleep disturbance is poorly recognized when patients have a mental disorder
[6,7].

The relationship between sleep and mental disorders is complex and not fully understood.
Sleep disturbance may precede depression
[8-10], and 40% to 70% of patients who are successfully treated for depression experience
sleep disturbance as a residual symptom
[11-13]. On the other hand, the remission rate following anti-depressive treatment can be
doubled if adjunct treatment for sleep disturbance is provided
[14], and depression can be treated using cognitive behavior therapy for insomnia alone
[15]. These findings challenge the assumption that the sleep disturbance is secondary
to a primary disorder. It may be better conceptualized as a comorbid condition, at
least in depression. In a state-of-the-science statement the National Institutes of
Health (NIH) recommended that when insomnia occurs concurrent with other disorders
it should be considered comorbid rather than secondary
[16]. In the online draft for the DSM-5, this recommendation is taken into consideration
and a paradigm shift is proposed as to how sleep disturbance should be conceptualized
in patients with mental disorders
[17]. It is suggested that insomnia should always be coded if the criteria are fulfilled,
regardless of meeting criteria for other disorders.

Most research so far on the association between sleep disturbance and mental disorders
have been conducted in selected patient groups, mostly depressed patients, that may
not fully resemble the heterogeneous group of patients found in public health care
systems. The clinical usefulness of the NIH recommendation to regard insomnia as a
comorbid disorder, rather than an epiphenomenon to a primary mental disorder, would
be further supported if it was demonstrated that sleep disturbance is associated with
distress and disability independently of the patients’ primary diagnosis also in settings
representative of mental health care. Studies investigating such associations may
be particularly relevant now with the advent of the DSM-5 proposal. However, no studies
have been conducted to test if sleep disturbance is associated with current clinical
state and benefit from treatment for patients representative of clinical settings.
The aim of the current study was thus to test the hypothesis that sleep disturbance,
independently of the patients’ primary mental disorder, is associated with variations
in quality of life, disorder and symptom severity, level of functioning, and benefit
from treatment in a large, heterogenous, clinical sample.

Method

Procedure

The data in this cross-sectional study were collected from eight general mental health
care centers during eight weeks in 2002 and four weeks in 2005. The data collections
were commissioned by the Norwegian Department of Health and conducted by an independent
research institution, SINTEF Technology and Society. One person was in charge of organizing
the data collection from both patients and clinicians at each center. The centers
were selected to be demographically representative for the country and the catchment
areas of the included clinics covered about 10% of the Norwegian population in both
urban and rural areas in different regions of the country. The assessments were the
same across all sites and in both years. The two data-sets were pooled into one for
the current study.

Participants

All 6538 patients receiving treatment in the mental health care centers were enrolled.
Patients who returned self-report questionnaires were included (N = 2246). Patients were between 18 and 85 years old. Mean age was 39.5 years (sd =
12.0).

Assessments

Patient rated assessments

Quality of life

Patients completed the Manchester Short Assessment of Quality of Life (MANSA)
[18]. The MANSA is designed to assess the quality of life of patients with mental disorders
and has satisfactory reliability and validity for this patient group
[18,19]. The MANSA comprises four objective and 12 subjective items and the subjective items
were used in this study. The items are designed to assess the satisfaction the patients
derive from the following domains: life as a whole, job, financial situation, number
and quality of friendships, leisure activities, accommodation, personal safety, people
the patient lives with (or living alone), sex life, relationship with family, physical
health, and mental health. The MANSA is rated on a 7-point Likert scale (1 = couldn’t
be worse, 7 = couldn’t be better). The score used in this study is the mean of the
12 items. 344 patients did not complete the MANSA. Cronbach’s alpha was 0.87 for the
included sample.

Symptom severity

Patients completed the Symptom Checklist – 25 (SCL-25) in 2002, and the Symptom Checklist
– 10 (SCL-10) in 2005. Both are short versions of the SCL-90-R, which has been extensively
used in research and clinical settings, and the Norwegian translations have satisfactory
reliability and validity
[20]. The SCL-25 consists of 25 items, and the SCL-10 consists of 10 items, describing
severity of psychiatric symptoms rated on a 4-point scale (1 = not at all, 2 = a little
severe, 3 = quite severe, 4 = very severe). All items on the SCL-10 are present in
the SCL-25 and only the SCL-10 items were used in the current study. 101 patients
did not complete the SCL-10 and the Cronbach’s alpha was 0.89 for the included sample.
A mean score of 1.85 or higher indicates mental disturbance on the SCL-10
[20].

Benefit from treatment

Patients evaluated the degree of benefit they had received from treatment at the time
of the study. The patients rated four domains using a 5-point Likert scale (1 = very
little benefit, 2 = rather little, 3 = neither little nor much, 4 = quite much, 5
= very much benefit). The four domains were: symptom reduction, symptom management
skills, practical day-to-day functioning, and ability to work. 154 patients did not
complete the treatment evaluation and Cronbach’s alpha for the four domains was 0.79
for the included sample.

Sleep disturbance

Three items measure sleep disturbance on the SCL-90R. On the SCL-25 and SCL-10, these
three items have been reduced to one item measuring severity of sleep disturbance
the past 14 days on a 1 to 4 likert scale (How much have sleep problems disturbed
you the past 14 days: 1 = not at all, 2 = a little severe, 3 = quite severe, 4 = very
severe disturbance). This item was used to assess patient rated level of sleep disturbance.
The use of such a simple dimensional measure of sleep quality is in accordance with
the proposals for field trials made by the DSM-5 Sleep-Wake Disorders Workgroup and
Advisors
[21].

Clinician rated assessments

Disturbance severity

The clinicians used the Health of Nations Outcome Scales (HoNOS) to evaluate the patients’
level of disturbance severity. The HoNOS is a 12-item clinician rated scale designed
to measure the health and social functioning of patients with mental disorders. It
has been widely used for patients in mental health care settings, and a review of
the studies on the psychometric properties concluded that the HoNOS has adequate reliability
and validity
[22] The HoNOS has four subscales, behavior problems, cognitive impairment, symptoms and
social functioning, and all items are rated on a 0 – 4 scale (0 = no problem, 1 =
minor problem requiring no action, 2 = mild problem but definitely present, 3 = moderately
severe problem, 4 = severe to very severe problem)
[23]. The sum score of the HoNOS was used to assess the level of disturbance severity.
Because the instructions on how to code item 8 (symptoms) where somewhat different
in the two data-sets, this item was omitted from the sum score in the main analyses.
The sum score of the HoNOS was 10.2 (SD = 4.9) for all 12 items on the HoNOS. Please
see Table
1 for the sum score the HoNOS with item 8 omitted. There were missing items on 442
patients on the HoNOS.

Table 1.Mean scores on the independent variables for the patients from eight public mental
health care centres who were included in the study

Global assessment of functioning

The clinicians used a split version of the Global Assessment of Functioning Scale.
The Global Assessment of Functioning Scale is described in Axis V of the Diagnostic
and Statistical Manual of Mental Disorders – IV (DSM-IV)
[4]. The split version is divided into one function score (GAF-F) and one symptom score
(GAF-S). This has been done because of skepticism concerning the use of a single scale
to measure both level of social and occupational function and severity of psychiatric
symptoms
[24]. The split version is reliable and consistent across raters
[25].

Functioning

The GAF-F is a clinician rated 0–100 scale measuring the social, occupational, and
psychological functioning of adults, e.g., how well or adaptively one is meeting various
problems in living. There were missing data for 301 patients on the GAF-F.

Symptom severity

The GAF-S was used to assess the patients’ overall level of symptom severity. The
GAF-S is a clinician rated 0–100 scale measuring the level of symptomatic distress
[25]. There were missing data for 301 patients on the GAF-S.

Improvement from treatment

Clinicians rated the level of improvement from the beginning of treatment to the point
of data collection on three domains using a 7-point Likert scale (1 = much worse,
2 = a little worse, 3 = no change, 4 = a little better, 5 = a bit better, 6 = much
better, 7 = very much better). The three domains were: psychiatric symptoms, practical
day-to-day functioning, and ability to work. Treatment improvement was not evaluated
for 188 patients and Cronbach’s alpha for the three domains was 0.81 for the included
sample.

Primary diagnoses

Patients were assigned one primary and up to two additional ICD-10
[5] diagnoses according to ordinary clinical practice. We used the primary diagnosis
in this study. Diagnoses were first grouped into the ten main diagnostic chapters
of the ICD-10 chapter 5: F0 Organic, including symptomatic, mental disorders; F1 Mental
and behavioral disorders due to psychoactive substance use; F2 Schizophrenia, schizotypal
and delusional disorders; F3 Mood disorders; F4 Neurotic, stress-related and somatoform
disorders; F5 Behavioral syndromes associated with physiological disturbances and
physical factors; F6 Disorders of adult personality and behavior; F7 Mental retardation;
F8 Disorders of psychological development; and F9 Behavioral and emotional disorders
with onset usually occurring in childhood and adolescence. Because few patients had
received any of the diagnosis of F0 Organic, F1 Substance related, F5 Behavioral Syndromes,
F7 Retardation, F8 Developmental, and F9 Childhood disorders, these patients were
grouped into one group entitled Other Disorders in the analyses (N = 175). 291 patients
had not received an ICD-10 diagnosis of mental or behavioral disorder at the time
of data collection. No patients had received a diagnosis of insomnia or any other
sleep related diagnoses as a primary or comorbid diagnosis.

Treatment duration

The number of months the patients had been in treatment at the time of the study was
14.5 months (sd = 28.7), whereas the median duration of treatment was 7 months.

Types of care

Patients were either receiving treatment as in-patients or out patients.

To examine differences in level of sleep disturbance in the different primary diagnostic
groups we performed a one-way analysis of variance (ANOVA). To test if there were
differences in levels of sleep disturbance between type of care, and men and women
we performed two independent t-tests.

Six of the seven dependent variables were normally distributed and used in six hierarchical
multiple regression analyses to test if sleep disturbance was related to the dependent
variables independently of age and gender, time in treatment, type of care and primary
diagnoses. We entered age and gender in step 1, time in treatment in step 2, type
of care in step 3, primary diagnostic groups in step 4, sleep disturbance in step
5, and the interactions between sleep disturbance and the primary diagnostic groups
in step 6. Because the variable “Clinician rated improvement from treatment” was not
normally distributed, and could not be normalized, we dichotomized this variable and
performed logistic regression analysis to test if sleep disturbance was related to
good or poor clinician rated improvement from treatment. Patients with worsening or
no improvement from treatment were classified as having “poor outcome” and patients
with various degrees of improvement were classified as having “good outcome”. The
logistic regression analysis was performed with the same hierarchical structure as
the linear regression analyses.

Because of the number of statistical analyses, we Bonferroni corrected the level of
significance to p < 0.007. Missing data was handled using listwise deletion. Mean score for the SCL
was calculated omitting the sleep item. The statistical analyses were performed using
PASW version 18 for Mac Os X.

Ethics

The study was approved by the Regional Ethical Committee for Research in Health and
by the Norwegian Data Inspectorate. The Directorate of Health and Social Affairs gave
consent for the use of information from the health services.

Results

Descriptive and preliminary analyses

Diagnostic distribution, type of care and gender is reported in Table
2 along with the mean scores and standard deviations on sleep disturbance for each
group.

Table 2.Descriptive and clinical data for patients from eight public mental health care centres
included in the study

Mean scores, standard deviations, and response rates on the dependent variables are
shown in Table
1.

Patients with an ICD-10 diagnosis of Schizophrenia (chapter F20) reported significantly
lower levels of sleep disturbance than other patients (F (4, 1942) = 11.9, p < 0.0001). Levels of sleep disturbance were not different between patients
in different types of care (t (2233) = 0.46, p = 0.64) or between men and women (t
(2195) = 1.51, p = 0.13).

Hypothesis testing

Level of sleep disturbance, entered in the fifth step of the regression analyses,
was significantly and uniquely associated with all the seven dependent variables.
See Table
3 for a summary of these results. The interactions between sleep disturbance and specific
diagnoses, entered in step 6, were not significantly associated with any of the dependent
variables.

Table 3.Summary of six linear hierarchical regression analyses and one logistic hierarchical
regression analysis assessing the unique associations between sleep disturbance and
the dependent variables adjusted for age, gender, time in treatment, type of care,
and diagnoses for patients from eight public mental health care centres

Discussion

Main findings

We found that higher levels of sleep disturbance were associated with significantly
lower quality of life, higher distress and functional impairment, and less benefit
from treatment for patients in mental health care, independently of their primary
diagnosis. To our knowledge, it is the first time this has been shown in a large sample
of patients representative of public mental health care clinics. These results might
encourage clinicians to assess and provide specific treatment for sleep disturbance
to patients with mental disorders as this might improve treatment results.

The DSM definition of a mental disorder is “a behavior or psychological syndrome that
is associated with present distress or disability”
[4]. Our results are in line with this definition, and with the recommendation from the
NIH
[16], and the suggested change in the DSM-5
[17], that sleep disturbance in patients with mental disorders may be regarded as a standalone
therapeutic entity comorbid to the primary mental disorder.

Interpretation in relation to previous research

The present study demonstrates associations between sleep disturbance and patient
rated quality of life and clinician rated disorder severity and level of functioning.
Quality of life has been defined as “a concept encompassing a broad range of physical
and psychological characteristics and limitations which describe an individual’s ability
to function and to derive satisfaction from doing so”
[26]. The MANSA measures the patients’ satisfaction with social, professional, physical
and emotional factors. The HoNOS measures mental and social functioning, whereas the
GAF measures the general level of functioning. As such, our combined results, encompasses
these broad features of quality of life laid out in the above definition. In 2005
the NIH recommended that future studies should focus on the association between quality
of life and sleep disturbance
[16], and emerging reports from the last years describe individuals with sleep disturbance
to have poor quality of life
[26,27] independently of somatic complaints
[27,28] and also when the sleep disturbance is comorbid to depression
[29]. Thus our study extends the current body of research by showing that sleep disturbance
is associated with poor subjective quality of life and functioning in all patient
groups in mental health care.

An important finding from the current study was that higher levels of sleep disturbance
were strongly associated with higher levels of psychiatric symptom severity as measured
by both clinicians and patients. This is similar to previous findings where patients
with primary insomnia report high levels of emotional distress
[30] and more negative affect
[31]. Depressed patients with insomnia also report higher levels of symptom severity than
depressed patients without insomnia
[29,32], and the current study extends these findings to patients with other mental disorders.
In sum, it is becoming more likely that sleep disturbance has a unique contribution
to patients’ level of psychiatric symptom severity, their daily functioning and their
quality of life that cannot be accounted for by the presence of other mental disorders.

The results from the present study also raise the question if sleep disturbance affects
treatment outcome. We found that higher levels of sleep disturbance were associated
with deriving less benefit from treatment as measured by both patients and clinicians.
These results are in line with previous research on the impact of sleep disturbance
on the treatment of depression. Untreated, sleep disturbance in depressed patients
predicts poorer response to psychotherapy
[33] and is the most common residual symptom after successful treatment of depression
[11,12]. On the other hand, providing specific treatment for insomnia for patients with major
depression who are receiving anti-depressant medication can enhance the effect of
the medication
[14,34] and improve quality of life
[35]. One study even found that only providing cognitive behavior therapy for insomnia
(CBT-I) to patients with mild depression normalized depression scores in 87% of the
patients
[15]. Interestingly, a recent pilot trial of CBT-I in 15 patients with persistent persecutory
delusions and comorbid insomnia gave very promising results. Treatment with CBT-I
did not only lead to large improvements in the insomnia of these patients but were
also associated with large improvements in persecutory delusions
[36]. There is less knowledge about the clinical impact of sleep in the treatment of anxiety
disorders. However, one study found that sleep does not improve after successful treatment
of panic disorder
[37]. Providing CBT-I for patients with Post Traumatic Stress Disorder (PTSD) can also
improve both sleep quality and other PTSD symptoms including nightmare frequency
[38]. Thus, from the body of research that has been conducted so far, it seems that treating
sleep disturbance may enhance treatment outcome, whereas no treatment for sleep disturbance
could result in poorer outcome. From the findings in the present study it would be
interesting for future research to explore if providing specific treatment of sleep
disturbance in any mental disorder can have similar positive results.

Indeed, an interesting finding from the current study was that sleep disturbance was
equally common in all diagnostic groups with the exception of schizophrenia, where
there was less. This is in line with a recent review highlighting sleep disturbance
as a potential transdiagnostic mechanism across mental disorders
[39]. From a neurobiological point of view, Harvey et al. proposes that there is a bidirectional
relationship between sleep disturbance and emotion regulation that may account for
how sleep disturbance and emotional distress are linked in mental disorders
[39]. Our finding is also similar to the conclusions of a meta-analysis of polysomnographically
measured sleep in psychiatric patients where no differences between diagnostic categories
could be found
[40]. The low frequency of self-reported sleep disturbance among patients suffering from
schizophrenia both in the present study and an earlier study
[41] might both be explained by selection of patients, problems with insight, and characteristics
of the illness.

Limitations

There are limitations to the study that should be noted. First, the treatment results
were rated retrospectively using rating scales that had not previously been validated.
Social desirability factors, expectancy effects, and the patients’ feedback might
have biased the clinician rated improvement scores and it is worth noticing that,
on average, the clinicians reported more favorable outcomes than the patients did.
This might explain why the clinicians’ rated outcomes were not normally distributed.
Second, there may be selection biases, as about two-thirds of the original sample
of patients did not agree to have their self-report linked to the clinician- report.
This could be an artifact of the procedures. The patients had to specifically indicate
that they wanted to have their scores linked to their clinicians’ ratings, rather
than having to indicate if they did not want to have their scores linked. This difference
could have had a large impact on patient participation
[42]. However, our sample of patients seems representative of patients in public mental
health care settings compared to findings from similar samples in other countries
using the same measures
[18,20,23,43-45]. Third, in the current study, the limited explained variance on some measures may
be due to the study design. The study was commissioned by the Norwegian department
of health to evaluate the state of the National mental health care system and was
not designed specifically to evaluate the effects of co-occurring sleep disturbance
in patients with mental disorders. Fourth, the cross-sectional design of the study
does not allow for conclusions about causality and we cannot elucidate the exact relationship
between sleep disturbance and symptom severity. Moreover, the study is not able to
identify the potential underlying mechanisms that might link sleep disturbance to
various mental disorders
[39]. Fifth, a single item measuring sleep disturbance was used. This means that we cannot
discern the relative impact of sleep onset or sleep maintenance problems or if the
patients experienced other kinds of sleep disturbance. Still, it is remarkable that
a single item measuring sleep disturbance had a significant effect on all included
dependent variables. Indeed, that a single item can be used to get significant results
is in line with previous research and may be useful for clinicians
[46]. The work-group for sleep disorders in the DSM-5 revision has recently called for
data from clinical settings with simple dimensional measures of sleep quality
[21]. To compensate for these limitations, future studies should have a prospective study
design where measurements are done before, during, and after treatment using validated
outcome measures and scales adjusting for social desirability.

Conclusions

In mental health care settings, sleep disturbance has a unique association with quality
of life, symptom severity, disorder severity, level of functioning, and benefit from
treatment over and above the effects of age, gender, time in treatment, type of care,
and primary diagnoses. Thus, sleep disturbance ought to be considered a stand-alone
therapeutic entity rather than an epiphenomenon of existing diagnoses for patients
receiving treatment in mental health care.

Competing interests

All authors declare that we do not have any conflicts of interest.

Authors’ contributions

HK conceptualized the report, did the data analyses, data interpretation, and wrote
the report. BH, KL, GM, and TCS conceptualized the report, did data interpretation,
and critical appraisals of the report. RG and TR made the study designs, conducted
the data collections, and made critical appraisals of the report. All authors read
and approved the final manuscript.

Acknowledgements

We would like to thank researcher Solfrid Lileeng who was responsible for the data
collection and to SINTEF Technology & Society for allowing us to use the data. The
data collection was funded by the Norwegian Department of Health. The report was written
with funding from the Norwegian ExtraFoundation for Health and Rehabilitation.